My long-term career goal is to establish a research program to understand the etiology and developmental consequences of attention-deficit/hyperactivity disorder (ADHD) comorbidities, with a particularly emphasis in sluggish cognitive tempo (SCT). As an initial step in developing this research program, I have led a series of studies examining whether ADHD and SCT are not only distinct statistically but also differentially or uniquely associated with youths' functioning. My pilot work shows that while SCT is associated with higher rates of ADHD inattention, depression, anxiety, and daytime sleepiness, SCT is nonetheless statistically distinct from these domains. I have also found that SCT symptoms are associated with both academic and social impairments, even after controlling for ADHD. Since SCT symptoms are statistically distinct from ADHD and are uniquely associated with a range of impairments, it has been argued that SCT may be disorder separate from ADHD. Moreover, the clinical significance of the SCT construct is underscored by preliminary data showing the presence of elevated SCT to predict a poorer response to psychostimulant medication in children with ADHD. This suggests that frequently-used, evidence-based ADHD treatments are inadequate for children with ADHD who also display SCT. These findings point to the importance of SCT and the need for systematic research investigating the etiology, external correlates, and developmental progression of SCT. I am currently a research faculty member within the Division of Behavioral Medicine and Clinical Psychology at Cincinnati Children's Hospital Medical Center (CCHMC), and the K23 mechanism will enable me to focus my time and effort to develop a career as an independent clinical researcher. As my research interests have evolved, I recognize the need to obtain additional training in neuropsychology and neurophysiology to allow for a more comprehensive, multi-modal examination of ADHD and SCT. My training objectives are intended to address critical gaps in my knowledge to prepare me for an independent research career. Specifically, I plan to (1) obtain expertise in brain-behavior relationships with a specific emphasis in neuropsychology, (2) gain knowledge in neuroscience and neuroimaging methods with a specific emphasis in magnetoencephalography (MEG) and electroencephalography (EEG), (3) obtain training in statistics and programming relevant to neuropsychological and neurophysiological research with pediatric populations, and (4) improve grant-writing skills and extend research dissemination. I will accomplish these training objectives through coursework, guidance from my mentors and consultants with expertise in particular components of my training plan, completion of my research project, and attendance at relevant seminars, workshops, and conferences. Completion of the training and career development plan will enable me to achieve my long-term goal to establish an independent career in patient-oriented research that significantly advances our understanding of SCT and ADHD comorbidity. In order to separate out the unique correlates of SCT, I propose a research project that will be the first study to directly compare children with elevated SCT (with and without ADHD) to typically developing children and children with ADHD-only using a multi-method neuroimaging and behavioral approach. My study will use recently-validated SCT measures to recruit 184 children (ages 8-12 years) into four groups (n = 46 per group): SCT-only, ADHD-only, SCT+ADHD, and typically developing controls. All children will complete a comprehensive assessment that includes a diagnostic interview assessing SCT, ADHD, and psychiatric comorbidities, intelligence and academic achievement testing, and a battery of neuropsychological tests. A subset of participants will perform a task assessing distinct attentional networks while undergoing MEG (co- registered with structural MRI), an optimal imaging methodology given its excellent spatial and temporal resolution. This project will allow me to identify the underlying dysfunctions and impairments that distinguish SCT from ADHD, in turn having clear relevance for theory, nosology, and intervention. Cincinnati Children's Hospital provides an excellent environment to facilitate my development as an independent investigator studying brain-behavior relationships in ADHD and SCT. An exceptional mentoring team has been assembled to support my training and career development. Under the direction of Dr. Jeffery Epstein (primary sponsor), the Center for ADHD is a world-class ADHD specialty center. Also at CCHMC, Dr. Jing Xiang (Director, MEG Center; co-mentor) and Dr. Dean Beebe (Director, Neuropsychology Program; co- mentor) will provide mentorship in MEG and neuropsychology, respectively. Drs. Leanne Tamm and James Peugh will provide on-site expertise in ADHD neuroimaging and statistics, respectively. Finally, Dr. Erik Willcutt (University of Colorado Boulder) and Dr. Sandra Loo (University of California, Los Angeles) will provide external expertise in how neuropsychological and neurophysiological methods can inform models of ADHD comorbidity specifically. The cumulative experiences laid out in my training plan will provide the foundation for an independent research program with the goal of receiving an R01 prior to the end of the K23 award.